Avogadro's Number and the Mole Concept Worked Examples Cheat Sheet

Key Facts

• Avogadro's number is $6.022 \times 10^{23}$, so $1\ \text{mol}$ of any substance contains $6.022 \times 10^{23}$ particles.
• To convert moles to particles, use $\text{particles} = \text{mol} \times 6.022 \times 10^{23}$.
• To convert particles to moles, use $\text{mol} = \frac{\text{particles}}{6.022 \times 10^{23}}$.
• Molar mass is the mass of $1\ \text{mol}$ of a substance and is measured in $\text{g/mol}$.
• To convert grams to moles, use $\text{mol} = \frac{\text{mass in g}}{\text{molar mass in g/mol}}$.
• To convert moles to grams, use $\text{mass in g} = \text{mol} \times \text{molar mass in g/mol}$.
• The molar mass of a compound equals the sum of the atomic masses of all atoms in its formula, such as $H_2O = 2(1.01) + 16.00 = 18.02\ \text{g/mol}$.
• In a balanced chemical equation, coefficients give mole ratios, such as $2H_2 + O_2 \rightarrow 2H_2O$ meaning $2\ \text{mol }H_2$ reacts with $1\ \text{mol }O_2$.

Vocabulary

Mole

A mole is a counting unit equal to $6.022 \times 10^{23}$ particles of a substance.

Avogadro's Number

Avogadro's number is $6.022 \times 10^{23}$, the number of particles in $1\ \text{mol}$.

Molar Mass

Molar mass is the mass of $1\ \text{mol}$ of a substance, usually written in $\text{g/mol}$.

Particle

A particle is the basic unit being counted, such as an atom, molecule, ion, or formula unit.

Formula Unit

A formula unit is the simplest whole-number ratio of ions in an ionic compound, such as $NaCl$.

Conversion Factor

A conversion factor is a ratio equal to $1$ that changes units, such as $\frac{6.022 \times 10^{23}\ \text{particles}}{1\ \text{mol}}$.